The North Atlantic Treaty Organization (NATO) was the treaty signed by the Western European countries along with Canada and the United States in April of 1949.
NATO is an intergovernmental military alliance which constitutes a system of collective defense whereby its member states agree to mutual defense in response to an attack made by an external party.
Its founding members were composed of 12 nations, namely; Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, Netherlands, Norway, Portugal, United Kingdom, and United States.
The Treaty was signed on 4th April 1949 and was first invoked in 2001 in the attacks on 9/11 to the World Trade Center and the Pentagon.
